Pentax K-3 Mark III vs. Fujifilm X-T3

Comparison

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K-3 Mark III image
vs
X-T3 image
Pentax K-3 Mark III Fujifilm X-T3
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Megapixels
25.73
26.10
Max. image resolution
6192 x 4128
6240 x 4160

Sensor

Sensor type
CMOS
CMOS
Sensor size
23.3 x 15.5 mm
23.5 x 15.6 mm
Sensor resolution
6213 x 4142
6277 x 4157
Diagonal
27.98 mm
28.21 mm
Sensor size comparison
Sensor size is generally a good indicator of the quality of the camera. Sensors can vary greatly in size. As a general rule, the bigger the sensor, the better the image quality.

Bigger sensors are more effective because they have more surface area to capture light. An important factor when comparing digital cameras is also camera generation. Generally, newer sensors will outperform the older.

Learn more about sensor sizes »

Actual sensor size

Note: Actual size is set to screen → change »
vs
1 : 1.02
(ratio)
Pentax K-3 Mark III Fujifilm X-T3
Surface area:
361.15 mm² vs 366.60 mm²
Difference: 5.45 mm² (2%)
X-T3 sensor is slightly bigger than K-3 Mark III sensor (only 2% difference).
Note: You are comparing cameras of different generations. There is a 3 year gap between Pentax K-3 Mark III (2021) and Fujifilm X-T3 (2018). All things being equal, newer sensor generations generally outperform the older.
Pixel pitch
3.75 µm
3.74 µm
Pixel pitch tells you the distance from the center of one pixel (photosite) to the center of the next. It tells you how close the pixels are to each other.

The bigger the pixel pitch, the further apart they are and the bigger each pixel is. Bigger pixels tend to have better signal to noise ratio and greater dynamic range.
Difference: 0.01 µm (0.3%)
Pixel pitch of K-3 Mark III is approx. 0.3% higher than pixel pitch of X-T3.
Pixel area
14.06 µm²
13.99 µm²
Pixel or photosite area affects how much light per pixel can be gathered. The larger it is the more light can be collected by a single pixel.

Larger pixels have the potential to collect more photons, resulting in greater dynamic range, while smaller pixels provide higher resolutions (more detail) for a given sensor size.
Relative pixel sizes:
vs
Pixel area difference: 0.07 µm² (0.5%)
A pixel on Pentax K-3 Mark III sensor is approx. 0.5% bigger than a pixel on Fujifilm X-T3.
Pixel density
7.11 MP/cm²
7.13 MP/cm²
Pixel density tells you how many million pixels fit or would fit in one square cm of the sensor.

Higher pixel density means smaller pixels and lower pixel density means larger pixels.
Difference: 0.02 µm (0.3%)
Fujifilm X-T3 has approx. 0.3% higher pixel density than Pentax K-3 Mark III.
To learn about the accuracy of these numbers, click here.



Specs

Pentax K-3 Mark III
Fujifilm X-T3
Crop factor
1.55
1.53
Total megapixels
26.78
Effective megapixels
25.73
26.10
Optical zoom
 
Digital zoom
Yes
ISO sensitivity
Auto (100-1600000)
Auto, 200 -12800 (expands to 100-51200)
RAW
Manual focus
Normal focus range
Macro focus range
Focal length (35mm equiv.)
Aperture priority
Yes
Yes
Max. aperture
Max. aperture (35mm equiv.)
n/a
n/a
Metering
Multi, Center-weighted, Highlight-weighted, Spot
Multi, Center-weighted, Average, Spot
Exposure compensation
±5 EV (in 1/3 EV, 1/2 EV steps)
±5 EV (in 1/3 EV steps)
Shutter priority
Yes
Yes
Min. shutter speed
30 sec
30 sec
Max. shutter speed
1/8000 sec
1/8000 sec
Built-in flash
External flash
Viewfinder
Optical (pentaprism)
Electronic
White balance presets
8
7
Screen size
3.2"
3"
Screen resolution
1,620,000 dots
1,040,000 dots
Video capture
Max. video resolution
3840x2160 (30p/​24p)
4096x2160 (60p/50p/30p/25p/24p)
Storage types
SD/SDHC/SDXC
SD/SDHC/SDXC
USB
USB 3.0 (5 GBit/sec)
USB 3.0 (5 GBit/sec)
HDMI
Wireless
GPS
Battery
D-LI90 Lithium-ion battery
NP-W126S lithium-ion battery
Weight
820 g
539 g
Dimensions
134.5 x 103.5 x 73.5 mm
132.5 x 92.8 x 58.8 mm
Year
2021
2018




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Diagonal

Diagonal is calculated by the use of Pythagorean theorem:
Diagonal =  w² + h²
where w = sensor width and h = sensor height

Pentax K-3 Mark III diagonal

w = 23.30 mm
h = 15.50 mm
Diagonal =  23.30² + 15.50²   = 27.98 mm

Fujifilm X-T3 diagonal

w = 23.50 mm
h = 15.60 mm
Diagonal =  23.50² + 15.60²   = 28.21 mm


Surface area

Surface area is calculated by multiplying the width and the height of a sensor.

K-3 Mark III sensor area

Width = 23.30 mm
Height = 15.50 mm

Surface area = 23.30 × 15.50 = 361.15 mm²

X-T3 sensor area

Width = 23.50 mm
Height = 15.60 mm

Surface area = 23.50 × 15.60 = 366.60 mm²


Pixel pitch

Pixel pitch is the distance from the center of one pixel to the center of the next measured in micrometers (µm). It can be calculated with the following formula:
Pixel pitch =   sensor width in mm  × 1000
sensor resolution width in pixels

K-3 Mark III pixel pitch

Sensor width = 23.30 mm
Sensor resolution width = 6213 pixels
Pixel pitch =   23.30  × 1000  = 3.75 µm
6213

X-T3 pixel pitch

Sensor width = 23.50 mm
Sensor resolution width = 6277 pixels
Pixel pitch =   23.50  × 1000  = 3.74 µm
6277


Pixel area

The area of one pixel can be calculated by simply squaring the pixel pitch:
Pixel area = pixel pitch²

You could also divide sensor surface area with effective megapixels:
Pixel area =   sensor surface area in mm²
effective megapixels

K-3 Mark III pixel area

Pixel pitch = 3.75 µm

Pixel area = 3.75² = 14.06 µm²

X-T3 pixel area

Pixel pitch = 3.74 µm

Pixel area = 3.74² = 13.99 µm²


Pixel density

Pixel density can be calculated with the following formula:
Pixel density =  ( sensor resolution width in pixels )² / 1000000
sensor width in cm

One could also use this formula:
Pixel density =   effective megapixels × 1000000  / 10000
sensor surface area in mm²

K-3 Mark III pixel density

Sensor resolution width = 6213 pixels
Sensor width = 2.33 cm

Pixel density = (6213 / 2.33)² / 1000000 = 7.11 MP/cm²

X-T3 pixel density

Sensor resolution width = 6277 pixels
Sensor width = 2.35 cm

Pixel density = (6277 / 2.35)² / 1000000 = 7.13 MP/cm²


Sensor resolution

Sensor resolution is calculated from sensor size and effective megapixels. It's slightly higher than maximum (not interpolated) image resolution which is usually stated on camera specifications. Sensor resolution is used in pixel pitch, pixel area, and pixel density formula. For sake of simplicity, we're going to calculate it in 3 stages.

1. First we need to find the ratio between horizontal and vertical length by dividing the former with the latter (aspect ratio). It's usually 1.33 (4:3) or 1.5 (3:2), but not always.

2. With the ratio (r) known we can calculate the X from the formula below, where X is a vertical number of pixels:
(X × r) × X = effective megapixels × 1000000    →   
X =  effective megapixels × 1000000
r
3. To get sensor resolution we then multiply X with the corresponding ratio:

Resolution horizontal: X × r
Resolution vertical: X

K-3 Mark III sensor resolution

Sensor width = 23.30 mm
Sensor height = 15.50 mm
Effective megapixels = 25.73
r = 23.30/15.50 = 1.5
X =  25.73 × 1000000  = 4142
1.5
Resolution horizontal: X × r = 4142 × 1.5 = 6213
Resolution vertical: X = 4142

Sensor resolution = 6213 x 4142

X-T3 sensor resolution

Sensor width = 23.50 mm
Sensor height = 15.60 mm
Effective megapixels = 26.10
r = 23.50/15.60 = 1.51
X =  26.10 × 1000000  = 4157
1.51
Resolution horizontal: X × r = 4157 × 1.51 = 6277
Resolution vertical: X = 4157

Sensor resolution = 6277 x 4157


Crop factor

Crop factor or focal length multiplier is calculated by dividing the diagonal of 35 mm film (43.27 mm) with the diagonal of the sensor.
Crop factor =   43.27 mm
sensor diagonal in mm


K-3 Mark III crop factor

Sensor diagonal in mm = 27.98 mm
Crop factor =   43.27  = 1.55
27.98

X-T3 crop factor

Sensor diagonal in mm = 28.21 mm
Crop factor =   43.27  = 1.53
28.21

35 mm equivalent aperture

Equivalent aperture (in 135 film terms) is calculated by multiplying lens aperture with crop factor (a.k.a. focal length multiplier).

K-3 Mark III equivalent aperture

Aperture is a lens characteristic, so it's calculated only for fixed lens cameras. If you want to know the equivalent aperture for Pentax K-3 Mark III, take the aperture of the lens you're using and multiply it with crop factor.

Crop factor for Pentax K-3 Mark III is 1.55

X-T3 equivalent aperture

Aperture is a lens characteristic, so it's calculated only for fixed lens cameras. If you want to know the equivalent aperture for Fujifilm X-T3, take the aperture of the lens you're using and multiply it with crop factor.

Crop factor for Fujifilm X-T3 is 1.53

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